Wireless station location detection
First Claim
Patent Images
1. A system, comprising:
- an access point (AP), wherein, in operation;
the AP transmits a frame;
stores a time of beginning of transmission, t0;
if an acknowledgement frame is received the AP stores a time of completion of receiving, t1; and
if the acknowledgement frame is not received after one or more frame transmissions, the AP denies future requests for access to a network from the station and sends an instruction to a network management module (NMM) to broadcast an address of the station to other APs in the network to allow the other APs to deny the station access; and
the NMM, coupled to the AP, including;
memory having a value, tfixed, stored therein, representing a known frame exchange component period of time, and a value, c, representing the speed of light;
a distance calculation engine, in operation, the distance calculation engine determining a distance, d, using a formula d=[(t1−
t0−
tfixed)/2]·
c, d representing an estimated distance of the AP from the station; and
a graphical display engine, wherein, in operation, the graphical display engine displays one or more predicted locations the distance, d, from the AP in a graphically rendered environment.
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Abstract
A technique for locating a device uses connectivity to find a distance between an access point (AP) and a device. The AP transmits a frame to a device and receives an acknowledgement frame from the device. The amount of time for a signal to pass between the AP and the device is estimated and multiplied by the speed of light to find the distance between the AP and the device.
616 Citations
18 Claims
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1. A system, comprising:
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an access point (AP), wherein, in operation; the AP transmits a frame; stores a time of beginning of transmission, t0; if an acknowledgement frame is received the AP stores a time of completion of receiving, t1; and if the acknowledgement frame is not received after one or more frame transmissions, the AP denies future requests for access to a network from the station and sends an instruction to a network management module (NMM) to broadcast an address of the station to other APs in the network to allow the other APs to deny the station access; and the NMM, coupled to the AP, including; memory having a value, tfixed, stored therein, representing a known frame exchange component period of time, and a value, c, representing the speed of light; a distance calculation engine, in operation, the distance calculation engine determining a distance, d, using a formula d=[(t1−
t0−
tfixed)/2]·
c, d representing an estimated distance of the AP from the station; anda graphical display engine, wherein, in operation, the graphical display engine displays one or more predicted locations the distance, d, from the AP in a graphically rendered environment. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method, comprising:
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transmitting a first message from a first access point (AP); if a second message, associated with the first message, is not received from the station, (1) disabling future access to a network by a station and (2) broadcasting an address of the station to a second AP in the network to allow the second AP to deny the station access; and predicting a location of the station if the second message is received from the station, comprising; calculating a time difference, Δ
t, between the start of transmission of the first message, t0 and receipt of the second message, t1, wherein Δ
t=t0−
t1.calculating roundtrip propagation time by subtracting one or more fixed periods of time from Δ
t for one or more components of a frame exchange;determining a distance d by multiplying the speed of light by half the round trip propagation time; and predicting a location of the station based on d. - View Dependent Claims (11, 12, 13, 14)
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15. A device, comprising:
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a radio; a propagation distance calculating engine; wherein, in operation; the radio sends a frame to a station, the propagation distance calculating engine records a time of start of transmission of the frame, when the radio does not receive an acknowledgement frame from the station, the device (1) denies future access to a network by the station through the device and (2) broadcasts an address of the station to other devices in the network to allow the other devices to deny access to the network by the station; and when the radio receives an acknowledgement frame from the station; the propagation distance calculating engine stores a time of completion of receiving the acknowledgement frame, and the propagation distance calculating engine calculates a distance by d=[(Δ
t−
tfixed)/2]·
c, c being the speed of light, Δ
t being the time of completion of receiving minus the time of start of transmission, and tfixed being a known frame exchange component period of time. - View Dependent Claims (16, 17, 18)
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Specification